Engineering topics
Pahlka, B.
Publications and source records attributed to Pahlka, B..
The Liquid Argon Purity Demonstrator
The Liquid Argon Purity Demonstrator was an R&D test stand designed to determine if electron drift lifetimes adequate for large neutrino detectors could be achieved without first evacuating the cryostat. We describe here the cryogenic system, its operations, and the apparatus used to determine the contaminant levels in the argon and to measure the electron drift lifetime. The liquid purity obtained by this system was facilitated by a gaseous argon purge. Additionally, gaseous impurities from the ullage were prevented from entering the liquid at the gas-liquid interface by condensing the gas and filtering the resulting liquid before returning to the cryostat. The measured electron drift lifetime in this test was greater than 6 ms, sustained over several periods of many weeks. Measurements of the temperature profile in the argon, to assess convective flow and boiling, were also made and are compared to simulation.
Extreme argon purity in a large, non-evacuated cryostat
Liquid Argon Time Projection Chambers (LArTPCs) show promise as scalable devices for the large detectors needed for long-baseline neutrino oscillation physics. Over the last several years at Fermilab a staged approach to developing the technology for large detectors has been developed. The TPC detectors require ultra-pure liquid argon with respect to electronegative contaminants such as oxygen and water. The tolerable electronegative contamination level may be as pure as 60 parts per trillion of oxygen. Three liquid argon cryostats operated at Fermilab have achieved the extreme purity required by TPCs. These three cryostats used evacuation to remove atmospheric contaminants as the first purification step prior to filling with liquid argon. Future physics experiments may require very large detectors with tens of kilotonnes of liquid argon mass. The capability to evacuate such large cryostats adds significant cost to the cryostat itself in addition to the cost of a large scale vacuum pumping system. This paper describes a 30 ton liquid argon cryostat at Fermilab which uses purging to remove atmospheric contaminants instead of evacuation as the first purification step. This cryostat has achieved electronegative contamination levels better than 60 parts per trillion of oxygen equivalent. The results of this liquid argon purity demonstration will strongly influence the design of future TPC cryostats.
Accelerator/Experiment Operations - FY 2013
The low-energy and high-energy neutrino beams, the SeaQuest beam, and the Test Beam in the Meson area were shutoff on May 1, 2012 to begin work on the accelerator upgrades for NOvA (ANU), and for overall accelerator system maintenance. The shutdown of the Main Injector ended July 30, 2013, with the startup of the Accelerator systems for commissioning. Vacuum issues in the Main Injector delayed Commissioning and neutrino running until September.
Accelerator/Experiment Operations - FY 2012
This Technical Memorandum (TM) summarizes the Fermilab accelerator and accelerator experiment operations for FY 2012. It is one of a series of annual publications intended to gather information in one place. In this case, the information concerns the FY 2012 MINOS and MINERνA experiments using the Main Injector Neutrino Beam (NuMI), the MiniBooNE experiment running in the Booster Neutrino Beam (BNB), and the Meson Test Beam (MTest) activities in the 120 GeV external Switchyard beam (SY120). Each section was prepared by the relevant authors, and was somewhat edited for inclusion in this summary.